Month: February 2021

How to wrap long lines, *without* splitting words. The input is a very long string, with no newlines:

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed eu laoreet turpis. Curabitur lacinia, risus ut rhoncus mattis, turpis lorem iaculis justo, nec ultrices arcu erat vitae felis. Pellentesque vulputate efficitur scelerisque. Etiam bibendum dignissim mauris

Query

<a href="https://docs.microsoft.com/en-us/powerquery-m/list-accumulate">List.Accumulate</a> is an aggregate function. I’m using it to “sum” — to add strings together. If the current line plus the next word is longer than 80 characters, then insert a newline first.

To find the length of the current line, I only want the length after the very last newline. Occurrence.Last returns the last match, else -1 if nothing is found.

let  
    LoremIpsum = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed eu laoreet turpis. Curabitur lacinia, risus ut rhoncus mattis, turpis lorem iaculis justo, nec ultrices arcu erat vitae felis. Pellentesque vulputate efficitur scelerisque. Etiam bibendum dignissim mauris",

    // calculate length of string *after* the rightmost newline
    Text_LengthAfterNewline = (string as text) as number =>
        let 
            posLastNewline = Text.PositionOf(string, "#(lf)", Occurrence.Last),
            posOffset = if posLastNewline <> -1 then posLastNewline else 0,
            deltaLen = Text.Length(string) - posOffset
        in
            deltaLen,

    // word wraps text
    Text_WordWrap = (string as text, max_width as number) as text =>
        let
            words = Text.Split(string, " "),
            accum_result = List.Accumulate(
                words, "", 
                (state as text, current as text) as text =>
                    let
                        len = Text_LengthAfterNewline(state) + Text.Length(current) + 1,
                        maybeNewline =
                            if len > max_width then "#(lf)" else "",

                        accum_string = Text.Combine({state & maybeNewline, current}, " ")
                    in 
                        accum_string
            )
        in
            accum_result,
    
    wrapped_text = Text_WordWrap(LoremIpsum, 80)
in
    wrapped_text

The final result is 80 characters wide or less

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed eu laoreet turpis.
Curabitur lacinia, risus ut rhoncus mattis, turpis lorem iaculis justo, nec
ultrices arcu erat vitae felis. Pellentesque vulputate efficitur scelerisque.
Etiam bibendum dignissim mauris

Validating lengths of each line

let
    Source = #"wrap lines",
    validate_lengths =
        let 
            lines = Text.Split(Source, "#(lf)"),
            lengths = List.Transform(
                lines,
                each [ String = _, Length = Text.Length(_) ])
        in
            Table.FromRecords(
                lengths,
                type table[String = text, Length = number],
                MissingField.Error )
in
    validate_lengths